OTHER TYPES OP WATER INCREMENT 63 



Between these limits water is slowly added to the body; below 

 0.11 M the water is mostly excreted and draws some salt from 

 bodily reserves with it ; at concentrations higher than 0.29 M the 

 water leaves the body faster than it enters, but some sodium chlo- 

 ride stays behind. It is clear that the mere infusion of fluid is no 

 guarantee that a positive load of water is established. The precise 

 relations to solute and to previous depletion determine what regu- 

 latory activities toward water come into play ; and the relations are 

 already sufficiently complex that no one is likely to predict the 

 responses to these types of water load from a knowledge of some 

 other type. 



If 3.4 M solution of sodium chloride is infused, the dog promptly 

 drinks water (Gilman, '37; Bellows, '39). The drinking itself 

 might be regarded as a criterion of water deficit, even though the 

 body weight meanwhile is increased. If 6.7 M solution of urea is 

 infused in equal volume, less drinking results ; is the deficit less? 



One distinction that is useful is between an absolute deficit and 

 a relative deficit, the latter representing a change in the proportion 

 of water to at least one, several, or all other constituents of the 

 body. In addition, an increment that is initially a relative deficit 

 may become during the processes of adjustment and metabolism a 

 relative excess, and vice versa. In both, however, recovery with 

 respect to water consists in net loss of water in excess and net gain 

 of water in deficit, for no other events constitute a restoration of 

 water content. The rule of procedure which emerges is that every 

 state of water content requires quantitative characterization by 

 rates of water exchanges at least. Other characteristics may be 

 studied to great advantage; such will be considered later (chap- 

 ter X). 



Whereas in the water exchanges considered in chapter II only 

 five chief paths are distinguished: urinary (sensible), evaporative 

 (insensible), fecal, ingestive, metabolic (oxidative) ; in the water 

 increments of other magnitudes and other types additional paths 

 may be involved. Water in loads above +10% of Bo arouses in- 

 tense salivation and actual large losses of water thereby (Weir, 

 Larson and Rowntree, '22), especially when pituitrin is also ad- 

 ministered (Theobald, '34). Vomiting is a response to rapid water 

 administrations, but only when the water is put into the alimentary 

 tract (Rowntree, '22). The partition of water exchanges among 

 paths thus shows large contrasts among the several types that have 

 been investigated. 



